UMTS (Universal Mobile Telecommunications System) is a third generation public land mobile telecommunication system. Various standardization bodies publish standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) publishes standards for GSM (Global System for Mobile Communications) and W-CDMA (Wideband Code Division Multiple Access) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) publishes standards for CDMA2000 (Code Division Multiple Access) based UMTS. Standard document 3GPP TS 22.129 addresses UMTS handover requirements between UTRAN (UMTS Terrestrial Access Network) and other radio systems, and is incorporated herein by reference.